The present invention relates to an excavating tooth for earth-digging equipment such as earth augers and the like, and a mounting arrangement therefor.
Typically, earth-digging machines employ boring heads having a plurality of teeth which dig into the earth being excavated. These teeth absorb most of the load encountered by the machine and are the portion of the machine most likely to be worn or broken. Accordingly, tooth configurations and mounting arrangements therefor have been developed to facilitate replacement of broken teeth. Reversible tooth arrangements also have been developed that permit a tooth worn on one side to be turned over and used on the other side.
Generally, such teeth include a distal cutting portion and a proximal portion that is configured for bolting the tooth to a holder such as a shank plate as disclosed in U.S. Pat. Nos. 2,952,085 and 3,063,175 to Petersen, for example. Typically, the proximal portion includes a pair of laterally spaced prongs that form a slot therebetween through which a bolt extends to connect the tooth to the tooth holder. A back wall is provided on the tooth holder behind the prong ends of the tooth as disclosed in U.S. Pat. No. 3,063,175 to Petersen, for example. This wall is intended to prevent tooth rotation about the rotational axis of the bolt. The tooth holder can be cast steel in which the back wall typically is formed in the holder during casting. Alternatively, the tooth holder can comprise a stamped steel plate, in which case a tab is generally welded to the plate to form the back wall of the tooth holder. However, due to manufacturing tolerances of the teeth as well as the tooth holder, both tooth prong ends generally do not seat against the back wall when the tooth is bolted to the holder. As a result, a substantial amount of the load on the tooth can be transferred to the holder through the bolt, thereby causing bolt failure and machine down time. Such spacing between the prong ends and the back wall also can result in tooth oscillation as contact is alternately made between each tooth prong and the back wall. The resultant cyclic impact between the prongs and the back wall can significantly reduce the life of the tooth. In addition, where the welded tab configuration is used to form the back wall, the load transferred from the tooth to the tab, can break the tab from the tooth holder. It is also noted that on the tooth holders that have back wall tabs welded to the plate, the bolt generally acts as a clamp and prevents the tooth from moving forward and away from the tab. However, if the bolt is loosened the slightest amount, as a result of vibration for example, the tooth can move forward such that the prongs are no longer in contact with the back wall. The tooth will then oscillate about the bolt and loosen the bolt even further. As a result, the tooth can fall off of the auger or simply loosen to the point where it becomes ineffective.